Responses
They are connected because of family ties but you can skip Hana to Ryuu without worrying.
None is the sequel of the other. They are both happening at the same time within two different yakuza families.
Hana to Ryuu's characters are not even mentioned in Kizuna. You discover the bonds only of you read Hana to Ryuu, so you won't miss anything if you only read Kizuna.
I haven't read both mangas yet but I 'd like to know if I can just skip reading Hana to Ryuu. I'm scared to read it because of the comments about the death of one character. If this is a sequel, how does the story connect? Sorry for asking